Indirect sum with reference to range on other sheet

Registration date
Monday March 11, 2013
Last seen
August 14, 2013
- Aug 14, 2013 at 08:21 AM

I have a workbook with 2 sheets

Weekoverzicht and Grafieken

The sheet weekoverzicht is populated by a macro.
The macro starts with deleting existing columns, to get a clean sheet again.

On the sheet Grafieken a number of totals are calculated from columns in Weekoverzicht.
The formulas I'm using are:

But because of the deletion of columns by my macro, these formulas lose their references.
I'm pretty sure I should use the function "INDIRECT" to prevent this from happening... but after trying some things and consulting other sources on the internet I couldn't get it to work.

The formula that comes closest to a working solution is:
If you take a look into the function arguments menu of the formula, it displays the correct value. But the value of the formula on the sheet is still #REF!

Is there anyone who could point me to the solution?

Thanks in advance,